This invention relates to a device for automatically separating a photosensitive sheet from an original for copying apparatus, particularly of the type using a diazo photo-sensitive sheet.
In a typical example of copying apparatus with which the present invention may be employed, an original to be copied and a photosensitive copy sheet are advanced, in surface-to-surface contact with each other, past a printing station where an image of the original is established on the copy sheet by exposure to light. As delivered from the printing station, the original and copy sheet are still in contact, and must be separated from each other, e.g. to enable subsequent developing treatment of the copy sheet. A separating device is accordingly disposed at a suitable locality in the common delivery path of the original and copy sheet beyond the printing station.
Heretofore, to effect automatic separation of a photosensitive sheet from an original in such copying apparatus, it has been customary to employ a device wherein a suction tank is provided both on the original side and on the photosensitive sheet side of the delivery path, to draw the original and photosensitive sheet apart by suction by means of blowers of large capacity.
In a device of the type described, the photosensitive sheet (herein also termed the copy sheet) is drawn by a suction force of the blower which is exerted on the sheet through openings formed in a suction plate of the suction tank and gaps formed between a plurality of belt elements making up a conveyor belt interposed between the plate and sheet for advancing the sheet. This device has a disadvantage in that, since there is a clearance between the photosensitive sheet and the suction plate, a large quantity of air tends to flow from outside into the suction tank through this clearance, and it becomes necessary to use a blower of a greater capacity than would otherwise be required, in order to permit the suction force of the blower to achieve satisfactory results in drawing the copy sheet without interference by the large quantity of air flowing from atmosphere into the suction tank.